FR2732109A1 - CONTROL UNIT FOR PROVIDING A SERVO MOTOR CONTROL UNIT WITH POSITION DATA THAT IS ADJUSTED TO TAKE ACCOUNT OF PROCESSING DELAYS - Google Patents

Abstract

In an encoder unit for interpolating analog signals, a data delay time which is due to the A / D conversion and the arithmetic processing time is eliminated in order to avoid deterioration of the control performance. There is provided a memory unit (10) which retains detected angular data and a compensation unit for the output (11) of the encoder unit (1) which compensates for the delay time, and predicts a change of position produced during the delay time based on the angular data obtained from the current sampling cycle and from previous sampling cycles, and the delay time is compensated for by adding the predicted position change to the current sampling data.

Description

ENCODER UNIT FOR PROVIDING A

  SERVOMOTOR CONTROL POSITION DATA YES IS

  ADJUSTED TO TAKE ACCOUNT OF PROCESSING DELAYS

  The present invention relates to an encoder unit for detecting a position on a machine tool or the like and a servomotor control unit for controlling a servomotor according to position data obtained from the encoder unit. To give the encoder unit a high resolution or to obtain an encoder unit of absolute value, a method is known, as described, by

  example, in the Patent Publication Gazette HEI.

  5-65827, in which analog signals such as sine waves and triangular waves which are to be output as a function of the angle of rotation and analog signals having a specified phase difference from the analog signals are subjected to an A / D conversion (from analog to digital) and the conversion result is interpolated by arithmetic operation. Figure 22 is a configuration diagram of a conventional encoder control apparatus according to the method described above. In FIG. 22, the reference number 1 designates an encoder unit which is installed on a servomotor 3 or on a mobile part of a machine. The motor drive unit 2 controls the servomotor 3 with a position command from an external source and

an output from encoder unit 1.

  The following describes the details of the encoder unit 1 and the motor drive unit 2 of FIG. 22. An amount of light emitted by an LED (light-emitting diode) 4A to reach the

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  light receiving devices 6A and 6B such as photodiodes and phototransistors is transformed by a stop plate 5 installed on a motor shaft or on a moving part of a machine, and the light receiving devices 6A and 6B generate

  signals proportional to the amount of light.

  These signals are analog signals such as sine waves or triangular waves which are 90 ° out of phase with each other. These analog signals are simultaneously maintained by sampling and holding circuits 7A and 7B

  and entered 8A and 8B A / D converters.

  The data digitized by the A / D converter are converted into the position data by an arithmetic unit 9 and transmitted to the motor drive unit 2. The arithmetic unit 9 includes a divider

and a ROM table.

  The operation of the motor drive unit 2 is described below. A subtractor 12 emits a difference between a position command and an output O (Tn) of the encoder unit 1, and a means 13 for controlling the position generates a speed order value as a function of this difference. A subtractor 14 emits a difference between the speed order value and the speed reaction value obtained by differentiating G (Tn) in a differentiator 19, and a speed control means 15 generates a current order value by function of this difference. A subtractor 16 emits a difference between the current order value and the current reaction value, and a current control means 17 generates a voltage order value as a function of this difference. A three-phase voltage generator means 18 by pulse width modulation emits a three-phase voltage in response to the voltage command

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  and controls the servo motor, which is a synchronous motor. More specifically, the three-phase voltage generator means by pulse width modulation determines a position of the magnetic poles of the motor from the output (Tn) of the encoder and emits a three-phase voltage as a function of the current position of the magnetic poles. In the current feedback loop, the three-phase alternating current is detected by current detectors 31A and 31B, converted into a torque component current in a three-phase AC d-q axis converter 20 and used to control the current. In this case, the three-phase AC axis converter d-q 20 determines the position of the magnetic poles of the motor from the output O (Tn) of the motor and performs a conversion into

  depending on the current position of the magnetic poles.

  A data processing sequence table of the conventional coder unit is shown in FIG. 23. The holding by sampling and holding circuits 7A and 7B is a generally cyclic holding according to a signal.

  request given by the motor drive unit 2.

  When a signal is maintained, the A / D converters 8A and 8B start the A / D conversion. After the execution of the A / D conversion, the datum is processed arithmetically by the arithmetic unit 9 and an angular datum O (Tn) at the instant Tn is emitted at the instant Tn + Td. Motor drive unit 2

  executes the command from time Tn + Td.

  This angular data is emitted in the form of

  serial signals in most cases.

  As described above, there is a long delay in the A / D conversion, the arithmetic processing and the serial communication from the

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  maintenance of analog signals until transfer of

  data to motor drive unit 2.

  As a speed detection method with compensation for delay time, a method as described, for example, in the Patent Application Disclosure Gazette SHO. 62-260574, is known to predict V (n + l) from a detected speed V (n-1)

  previously and a speed Vn currently detected.

  In this case, the relation is represented by the following arithmetic equation: V (n + l) = 2V (n) - V (nl) This compensation method is intended to perform a linear extrapolation for linear increase or linear decrease represented on Figure 24. A block diagram for applying this compensation method to the position detection of the encoder unit to predict and compensate the sampling cycle TO (o TO = Tn - Tn-1) and the delay time Td is shown in Figure 26 and a block diagram of the compensation unit is shown in

figure 28.

  One can also easily imagine a curvilinear extrapolation process based on the assumption that a component of variation in the sampling cycle increases or decreases at an increment or

  specified decrement, as shown in Figure 25.

  In this case, the relation is represented by the following arithmetic equation: V (n + l) = 3V (n) - 3V (nl) + V (n-2) A schematic diagram for applying this method to the detection of position of the encoder unit to reduce and compensate the sampling cycle TO and the delay time Td is shown in Figure 27, and a block diagram of the compensation unit is

shown in figure 29.

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  By the very fact that the conventional coder unit is constructed as described above, there is a delay time before the position data is

  issued in response to a request from a servo

  amplifier. The position data transmitted therefore does not coincide with a true angle and contains a delay time. The motor drive unit 2 controls the motor as a function of the position data with such a delay. While the position control means 13 has had a low loop gain from the control system and is seldom affected by the delay time, the speed control means 15 has a high loop gain and requires him to provide high frequency responses; the delay time in the encoder output, which causes the same delay time in the speed control, therefore causes a deterioration of

the performance of the control.

  When a synchronous motor is used as a servomotor, the position data of the magnetic poles of the motor is necessary for the means 18 three-phase voltage generator by pulse width modulation and for the axis converter dq of AC three-phase, as described upper. However, there is a problem that, if the encoder output data contains a delay, the detection error of the magnetic pole, in particular in a high speed rotation of the motor, becomes large and

  that the engine output torque is greatly reduced.

  The above problems can be mitigated by accelerating the A / D conversion and the arithmetic operation. However, this mode of solution is disadvantageous in that it is necessary to use a high speed A / D converter and an arithmetic processing unit, which are very

expensive.

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  In addition, the reliability of serial communication at

high speed is limited.

  The following describes the problems resulting from using the compensation method shown in Figs. 28 and 29 to predict and calculate a position change that occurs during the detection delay. For example, as shown in FIGS. 30 and 31, it is assumed that the engine is stopped at a position 00 close to the border line between 00 and 01 until time Tn-1, then it passes through the region of position 01 crossing the border line at time Tn then returns to the initial position at time Tn + l. In this case, the convenient assumption is taken (delay time Td) = (sampling cycle TO). In the case of compensation by linear extrapolation, the equations are as follows: O (Tn + 1) = 20 (Tn) - O (Tn-1) = 2 O (Tn + 2) = 20 (Tn + l) O ( Tn) = -1 The encoder output fluctuates within three pulses despite the fact that the actual behavior of the motor is less than the minimum detection unit. This fluctuation is returned in response to the motor drive unit 2 to result in an increase in vibration when the engine is stopped. In the case of a compensation by curvilinear extrapolation represented on figure 29, the equations are as indicated below: G (Tn + l) = 30 (Tn) - 30 (Tn-1) + O (Tn-2) = 3 O (Tn + 2) = 30 (Tn + l) - O (Tn) = -3 As shown in figure 32, the output of the encoder fluctuates in a width of six pulses for

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  cause a further increase in vibration

when the engine is stopped.

  The position of the motor cannot be detected smoothly, even in a low speed movement of the motor for a relation to the minimum detection unit of the encoder unit and, if the compensation shown in the figures occurs. 28 and 29, an error lower than the minimum detection unit is amplified and outputted to accentuate the irregularity of the rotation. This phenomenon is shown in Figure 33. In Figure 33, there is shown by way of example an operation to accelerate in reverse after the speed has been reduced to zero. Vertical scales designate the encoder detection boundaries and the scales

  horizontal lines indicate the sampling time.

  As described above, the conventional method for predicting and compensating for delay time cannot

  be directly applied to the encoder unit.

  An object of the present invention is to solve the aforementioned problems by realizing: an encoder unit capable of outputting position data free of delay and of performing precise position detection; and a servomotor control unit capable of controlling the servomotor very precisely as a function of the data of

  position received from the encoder unit.

  To overcome the aforementioned problems, the servo control unit described herein includes an encoder unit which includes means for compensating for the encoder output which uses the position data obtained from the current sampling and the previous samplings to predict a change of position of a detected object (for example a servomotor) during a delay time necessary for

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  transmit position data from sampled analog detection signals. The encoder output compensation means outputs a predicted position change that occurs during the delay time, as well as predicted position data obtained by adding the predicted position change to the

  position data currently sampled.

  The servomotor control unit further comprises a motor drive unit comprising: position control means for generating a speed command value in response to a difference between a position command and the position data currently sampled; speed control means for generating a current order value in response to a difference between the speed order value and a speed reaction value obtained from the changed predicted position; conversion means for converting a three-phase alternating current detected on the servomotor into a torque component current, and for carrying out the conversion as a function of a current position of the magnetic poles in the case where the servomotor is a synchronous motor; current control means for generating a voltage command value in response to a difference between the current command value and a current reaction value generated by the conversion means; and voltage generator means for emitting a three-phase voltage in response to a current position of the magnetic poles

  based on the predicted position data.

  According to a first embodiment, the encoder output compensation means calculates the predicted position change that occurs during the delay time necessary to sample analog signals and transmit position data, by selecting the smallest of the values. following:

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  the absolute value of the position change in the current sampling cycle; and the absolute value of the position change in the previous sampling cycle, assuming that the position change during the sampling cycle varies linearly or curvilinearly relative to the position depending on the selected position change, and for

  compensate for the output position data.

  According to a second embodiment, the means for compensating the encoder output calculates the predicted position change which occurs during the delay time necessary to sample analog signals and transmit position data, by selecting: 1) the most small of the following values: the absolute value of the position change in the current sampling cycle, and the absolute value of the position change in the previous sampling cycle; and 2) the smallest of the following values: a difference between the change of position in the current sampling cycle and the change of position in the previous sampling cycle, and a difference between the change of position in the sampling cycle previous sampling and the change in position in the sampling cycle that occurred before the previous sampling cycle, and assuming that the change in position in the sampling cycle varies linearly or curvilinear depending on the sum of the selected position change and the difference of

  change of selected position.

  According to a third embodiment, the means for compensating the output of the encoder calculates the predicted change of position which occurs during the

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  delay time required to sample the analog signals and to transmit the position data, assuming that the change of position during the sampling cycle varies linearly or curvilinearly as a function of an average value of the change of position during the current sampling and position change

  during the previous sampling cycle.

  According to a fourth embodiment, the means for compensating the encoder output calculates the predicted position change which occurs during the delay time necessary to sample analog signals and transmit position data, assuming that the position change during the sampling cycle varies linearly or curvilinearly depending on the sum of an average value of the changes in position obtained from the change of position in the current sampling cycle and the change of position in the sampling cycle which occurred before the previous sampling cycle, and an average value of the differences between the position change in the previous sampling cycle and the position change in the sampling cycle that occurred

  produced before the previous sampling cycle.

  According to a fifth embodiment, the encoder output compensation means calculates a predicted position change from position data obtained in the current and previous samples, and it includes a variable multiplier used to reduce the predicted position change when the position change in the current sampling cycle is small. According to a sixth embodiment, the encoder output compensation means evaluates in advance a

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  l1 relation between a current value intended to be emitted by the drive unit of the motor and a degree of variation of the change of position in the sampling cycle, and calculates the predicted change of position which occurs during the time of delay, based on the evaluated relationship and the position data

currently sampled.

  According to a seventh embodiment, there is provided: a signal generator means serving to generate analog signals which correspond to an angle of rotation of a rotating shaft; A / D conversion means for sampling the analog signals and converting them into digital data; arithmetic operation means for obtaining an angle of rotation of the rotating shaft from the converted digital data; pulsed signal generator means for generating pulses whose phases are offset by 90 relative to each other; a counter for counting the number of said pulses; and a means of compensating the output of the encoder used to emit a sum of: 1) an angle of rotation measured by the counter from the sampling of the analog signals until the execution of the calculation of the angle of rotation , and 2) an angle of rotation calculated from the signals

  analog and constituting a current angle.

  Figure 1 is a block diagram showing the encoder unit and the servo motor control unit according to the

present invention.

  Figure 2 is a sequence diagram showing the operation of the encoder unit shown in

Figure 1.

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  Figure 3 is an illustration showing the operation of the memory unit of the memory unit.

  encoder according to the present invention.

  FIG. 4 is a block diagram showing the encoder unit and the servomotor control unit according to the

  first embodiment of the invention.

  FIG. 5 is a block diagram showing the compensation unit for the output of the encoder unit according to the

  first embodiment of the present invention.

  FIG. 6 is a block diagram showing the compensation unit for the output of the encoder unit according to the

  second embodiment of the present invention.

  Figure 7 is a flowchart showing the operation of the switches of the encoder unit

according to the present invention.

  FIG. 8 is a block diagram showing the compensation unit for the output of the encoder unit according to the

  third embodiment of the present invention.

  FIG. 9 is a block diagram showing the compensation unit for the output of the encoder unit according to the

  fourth embodiment of the present invention.

  FIG. 10 is a graph showing the operation at a position close to the detection boundary of the compensation unit of the output of the encoder unit according to the first and third modes

  of the present invention.

  FIG. 11 is a graph showing the operation at a position close to the detection boundary of the compensation unit for the output of the encoder unit according to the fourth mode of

  realization of the present invention.

  Fig. 12 is a graph showing the operation of the compensation unit of the output of the encoder unit according to the first and second

  embodiments of the present invention.

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  Fig. 13 is a graph showing the operation of the compensation unit of the output of the encoder unit according to the third and fourth

  embodiments of the present invention.

  Fig. 14 is a block diagram showing the compensation unit for the output of the encoder unit according to

  the fifth embodiment of the invention.

  FIG. 15 is a graph showing an example of operation of the variable multiplier of the output compensation unit shown in the

figure 14.

  FIG. 16 is a graph showing another example of operation of the variable multiplier of the output compensation unit shown in the

figure 14.

  Fig. 17 is a block diagram showing the encoder unit and the servo motor control unit according to the sixth embodiment of the present invention. Fig. 18 is a graph showing the function estimation unit of the coder unit

shown in Figure 17.

  FIG. 19 is a block diagram showing the encoder unit according to the seventh embodiment of the

present invention.

  FIG. 20 is an illustration showing the stop plate of the encoder unit shown in the

figure 19.

  Figure 21 is a time diagram showing the operation of the encoder unit shown in the

figure 19.

  Fig. 22 is a block diagram showing the conventional encoder unit and servo motor control unit. Figure 23 is a time diagram showing the

  operation of the conventional encoder unit.

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  FIG. 24 is a graph illustrating the classic example of compensation for the delay time in the

speed detection.

  FIG. 25 is a graph showing the classic example of compensation for the delay time in the

speed detection.

  FIG. 26 is a graph illustrating the compensation operation when the conventional compensation for the delay time is applied to the unit of

coder.

  Fig. 27 is a graph illustrating the compensation operation when the conventional delay time compensation is applied to the encoder unit. Figure 28 is a block diagram showing the configuration when conventional compensation of the

  delay time applies to the encoder unit.

  FIG. 29 is a block diagram showing the configuration when the conventional compensation of the

  delay time applies to the encoder unit.

  FIG. 30 is a diagram which illustrates the problem which arises in conventional compensation of the

delay time.

  FIG. 31 is a graph illustrating the problem which arises in conventional compensation of the

delay time.

  FIG. 32 is a graph illustrating the problem which arises in conventional compensation of the

delay time.

  Figure 33 is a graph illustrating the operation of conventional delay time compensation. The embodiments of the present invention are described in detail below. Figure 1 is a configuration of an encoder unit and a

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  actuator control according to the present invention.

  In FIG. 1, the elements which correspond to identical elements represented in FIG. 22 are designated by the same reference numbers and we omit

  to give a description. An output O (Tn) of a

  arithmetic unit 9 (which is the arithmetic operation means) is transmitted to a motor drive unit 2 and to an encoder output compensation unit (hereinafter called the output compensation unit 11 which is the means of compensation of the output), and is stored in a memory unit 10. The memory unit 10 stores the n most recent position data as shown in FIG. 3 and transmits a position data stored as a function of a request from the output compensation unit 11. The output compensation unit 11 transmits predicted position data O (Tn + Td) at an instant Tn + Td, which is compensated for an equal delay at a delay time Td in arithmetic operation and a predicted position change AO (Tn + Td) in the sampling cycle at the instant Tn + Td, based on a data of past sampling position O (Tn-1 ),

  O (Tn-2), ... and the current position data O (Tn).

  The output compensation unit 11 is a delay time compensation unit of the type shown in Figs. 28 and 29, or an output compensation unit shown in the first to sixth embodiments. The loop gain in position control is usually small (around 30 rad / s) and is

  rarely affected by delayed detection time.

  If imprecise data is returned as a reaction

  in the description of the classic compensation of the

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  delay time, the reaction data increases the irregularity of the vibration and speed. For this reason, the current position data O (Tn) is entered in the subtractor 12 of the motor drive unit 2 and used for the control

of position.

  A speed reaction value is generated by dividing the predicted position change AO (Tn + Td) in the sampling cycle at time Tn + Td by the sampling cycle TO in a divider 31 and is used to speed control. Data which is free of delay time is therefore used in the speed control with high loop gain to avoid deterioration of the performance of the control. Although a three-phase voltage generator means 18 by pulse width modulation (which is a voltage generator means), and a three-phase AC dq axis converter 20 (which is a conversion means) are not affected by a small position error and by irregular detection results, a large position deviation due to the delay time will cause a reduction in the motor torque and, for this reason, the predicted position data O (Tn + Td) is used at the instant Tn +

Td free of delay time.

  A data processing sequence diagram of the encoder unit according to the present invention is shown in Figure 2. Although the operating timings of all blocks are the same as those found in the classic example shown in FIG. 23, the data to be transmitted is the position data at time Tn + Td when the data output is completed and the delay time is eliminated.

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  First embodiment The first to sixth embodiments show the internal embodiments of the output compensation unit 11. Since these embodiments are intended to solve the problems of the conventional delay time compensation method, the overall configuration of the encoder unit can be the configuration described above represented in FIG. 1 or a configuration which transmits only the position data O (Tn + Td) which is compensated for by

  delay time as shown in Figure 4.

  Fig. 5 is a configuration diagram showing a compensation unit for the output of an encoder unit according to the first embodiment of the present invention. In FIG. 5, the subtractor 21A emits a difference between the current sampling position e (Tn) and the previous sampling position O (Tn-1), that is to say a change of position AOn during the current sampling cycle. The subtractor 21B emits a difference between the previous sampling position O (Tn-1) and a sampling position which precedes the previous sampling position (at time n-2) O (Tn-2), c 'is to say a change of position ASO (n - 1) in the previous sampling cycle. The smallest of the values AOn and AO (n - 1) is selected by the selector switch 22 as the current position change, which is to enter the multiplier 23. A position change between the instants Tn and Tn + Td is obtained by multiplying the selected position change AO by Td / T0 (remember that TO is the sampling time) in the multiplier 23. The

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  compensation for the delay time is carried out by adding the output obtained to O (Tn) in the adder 24. The operation flow diagram of this selector switch 22 is shown in FIG. 7. If the sign of ASOn differs from that of AO (n - 1), we give Ai = 0, and if their signs are the same, the smallest

absolute value is taken for A0.

  In this embodiment, an exit position obtained when the position deviates from a situation close to the detection border to cross the border, as shown in FIG. 30, is represented in FIG. 10. Being given that ASOn = 1 and that A0 (n 1) = 0 at the moment Tnt ASOn = 0 is selected by switch 22. In

  Consequently, we obtain the output O (Tn + 1) = O (Tn) = 1.

  Similarly, O (Tn + 2) = O (Tn + 1) - 0 is obtained, an incorrect output is returned to the motor drive unit 2 as shown in Figure 31 to prevent the vibration of the motor from growing . The behavior in movement at low speed is such that the position output is smoothed to avoid the increase in the ripple of the speed in the rotation of the motor.

  as shown in figure 12.

  Thus, according to the first embodiment, the output compensation means of the encoder therefore predicts a change in position which occurs during the delay time necessary to sample analog signals and transmit the position data, by selecting the smallest absolute values of the change of position obtained during the current sampling and the change of position obtained in the previous sampling. The calculation is carried out on the assumption that the change of position in the sampling cycle varies linearly or

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  curvilinearly depending on the selected position change. By compensating the position data in this way, we obtain a position data of

more precise output.

  Second embodiment Fig. 6 is a configuration diagram showing a compensation unit for the output of an encoder unit according to a second embodiment of the present invention. In Figure 6, we have omitted

  give the description of the same components as those of

  the compensation unit for the output of the first embodiment shown in FIG. 5. The switch 22A selects the relevant position change AO as the switch 22 for the compensation unit for the output of the first embodiment. The subtractor 25A emits a difference A (tOn) between the change of position AOn in the current sampling cycle and the change of position AO (n - 1) in the previous cycle. Subtractor 25B emits a difference A (AOn - 1) between the change of position AO (n - 1) in the previous sampling cycle and the change of position AO (n - 2) in the (n-2) th cycle sampling. Switch 22B selects the smallest of the values A (AOn) and A (AOn - 1) as A (AOn), according to the flow diagram shown in Figure 7 (i.e., switch 22B operates in the same way, as regards its inputs, as the switch 22 of the first embodiment). The sum of the selected position change AO and the increment A (AO) of the position change is multiplied by Td / T0 in the multiplier 23 to provide a position change between Tn and Tn + Td. The delay time is

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  compensated by adding its output to O (Tn) in

the adder 24.

  In this embodiment, FIG. 10 shows an exit position obtained when the position deviates from the state of the situation near the detection border in order to cross the border as shown in FIG. 30. that AOn = 1 and AL (n - 1) = 0 at time Tn, AOn = 0 is selected by switch 22 and, given that A (AOn) = 1 and A (AGn - 1) = 0, A (AO) = 0 is selected by switch 22B. Consequently, the output O (Tn + 1) = 1 is obtained. Similarly, O (Tn + 2) = 0 is given, an incorrect output is returned to the motor drive unit 2 as shown in the figure 32 to prevent engine vibration from growing. The behavior in low speed movement is such that the position output is smoothed to avoid increasing the speed ripple in the

  motor rotation, as shown in figure 12.

  Thus, according to the second embodiment, the means of compensating for the output of the encoder therefore predicts a change of position which occurs during the delay time necessary to sample analog signals and transmit the position data, by selecting the most smallest of the absolute values of the position change in the current sampling cycle and the position change in the previous sampling and the smallest of the values of a difference between the position change in the current sampling cycle and the change position in the previous sampling cycle and a difference between the change of position in the previous sampling cycle and the change of position in the (n-2) th sampling cycle. The calculation is performed by taking

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  assuming that the change of position in the sampling cycle changes linearly or curvilinearly depending on the sum of the differences between the selected position changes. By compensating the position data in this way, we obtain a position data of

more precise output.

  Third embodiment Fig. 8 is a configuration diagram showing a compensation unit for the output of an encoder unit according to a third embodiment of the present invention. The subtractor 21 emits a difference between the current sampling position

  O (Tn) and the (n-2) th sampling position O (Tn-

  2), that is to say a change of position 2AO in two sampling cycles, and enters it into the adder 23. We derive an average position change of two sampling cycles by multiplying by 1 / 2 in the multiplier 23 and, at the same time, a change of position between Tn and Tn + Td is obtained by multiplying the output by Td / T0. The delay time is compensated for by adding its output to O (Tn) in

the adder 24.

  In this embodiment, in FIG. 10 is shown an exit position obtained at the time when the position deviates from the situation close to the detection border in order to cross the border as shown in FIG. 30. output at time Tn is 2AOn = 1 and the output O (Tn + 1) = 1 is obtained by removing the fraction of the average value and adding it to 0 (Tn). Likewise, 0 (Tn + 2) = 0 is given and an incorrect output is returned to the motor drive unit 2 as shown in Fig. 31 to prevent the vibration of the motor from

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  croltre. The behavior in the movement at low speed is such that the position output is smoothed to prevent the growth of the ripple of the rotational speed of the motor as shown in FIG. 13. Thus, according to the third embodiment, the means compensation of the encoder output therefore predicts a change of position which occurs during the delay time necessary to sample analog signals and transmit position data, assuming that the change of position varies linearly or curvilinearly as a function of 'an average value of a change of position in the current sampling cycle and a change of position in the previous sampling cycle. By compensating the position data in this way, more precise output position data are obtained. Fourth embodiment Fig. 9 is a configuration diagram showing a compensation unit for the output of an encoder unit according to a fourth embodiment of the present invention. The subtractor 21D performs the same operation as the subtractor 21 of the compensation unit for the output of the previous embodiment and it emits a change of direction 2A8 in two sampling cycles. The subtractor 21A emits the change of position AOn in the current sampling cycle, the subtractor 21C emits the change of position AO (n - 2) and the subtractor 25 emits a component of variation 2A (AO) of the change of position in two sampling cycles. 2AO and 2A (AO) are added to the adder 26 and entered into the multiplier 23. A change in

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  mean position and the variation component of the change of position of two sampling cycles by multiplying the output by 1/2 in the multiplier 23 and, at the same time, we obtain a change of position between Tn and Tn + Td by multiplying the output by Td / T0. The delay time is compensated for by adding its

  output at 0 (Tn) in adder 24.

  In this embodiment, in FIG. 11 is shown an exit position obtained when the position deviates from the situation close to the detection border in order to cross the border as shown in FIG. 30. 2AO = 1 and 2A (AO) = 1 at time Tn are added to the average value O (Tn + l) to obtain O (Tn + l) = 2. Likewise, O (Tn + 2) = 0 is given and an output incorrect is returned to the motor drive unit 2, as in the classic example shown in Figure 32 to prevent the vibration of the motor from growing. The behavior in movement at low speed is such that the position output is smoothed to prevent the increase in speed ripple in the

  motor rotation as shown in figure 13.

  Thus, according to the fourth embodiment, the means for compensating the output of the encoder therefore predicts a change in position which occurs during a delay time necessary to sample analog signals and transmit position data, assuming that the change of position varies linearly or curvilinearly as a function of the sum of the average value of the changes of position obtained from the changes of position in the current sampling cycle and the previous sampling cycle, and from an average value of differences in position change in the previous sampling cycle and the (n-2) th

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  sampling cycle. By compensating the position data in this way, we obtain

more precise exit position.

  Fifth embodiment Fig. 14 is a configuration diagram showing a compensation unit for the output of an encoder unit according to a fifth embodiment of the present invention. We failed to give the

  description of the components which are the same as those

  of the output compensation unit shown in FIG. 28. Reference number 27 designates a second multiplier which multiplies the output of the multiplier 23 by K (AOn) and its output is added to O (Tn) by the adder 24 to compensate for the delay time. In this case, the multiplier 27 is a variable multiplier for which the amplification K (AOn) varies with the value of AOn. This multiplier K (AOn) is set to be large when the position change during the sampling interval is large and to be small when the position change during the sampling interval is small. In other words, by providing this variable multiplier in addition, the amplification of the compensation is set at a low value for low speed operation in which the effect of the delay time is small and a small detection error can adversely affect the control loop and increase the vibration and speed irregularity, and to be great for high speed operation, in which the effect of the delay time is large and a small detection error rarely adversely affects the control loop. In this way, problems such as the increase in vibration due to the classical compensation of the time of

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  delay are resolved at the same time that the

problem due to delay time.

  Figures 15 and 16 are respectively a graph showing an example of operation of the variable multiplier 27 and o the amplification from 0 to 1 can be modified by continuous variation with respect to AO as shown in Figure 15, and in the case where l amplification from 0 to 1 can be modified by variation in several steps, for example in two or more steps as shown in FIG. 16. Although the prediction of the position has been described in the first to fifth embodiments assuming that the position varies linearly, the configuration can be chosen so that the position varies

curvilinearly.

  Thus, according to the fifth embodiment, the means for compensating the output of the encoder predicts a change of position which occurs during the delay time necessary to sample analog signals and transmit a position data based on the position data obtained. in the current sampling cycle, the previous and still earlier sampling cycles. The encoder output compensation means is equipped with a variable multiplier to obtain a more precise position output by reducing the predicted position change when the position change in

  the current sampling cycle is small.

  Sixth embodiment Fig. 17 is a configuration diagram showing an encoder unit and a servo motor control unit according to a sixth embodiment of the present invention. The components of the encoder unit and the servomotor control unit which are common to those of embodiment 1 shown in

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  Figure 1 are designated by the same numbers

  reference and omits to give a description. The

  reference number 28 designates a unit for estimating the function A (AO) - Iq which obtains a state variation A (AO) of the change in position with respect to the sampling position data O (Tn) and the data of the two preceding sampling positions e (Tn-1) and O (Tn-2) which are stored in the memory unit 10. The unit for estimating the function A (AO) - Iq estimates a function between the value of the current Iq emitted by the drive unit of the

  motor and variation A (A) as shown below.

  A (AO) = f (Iq) We estimate a function which represents a substantially average gradient of the relationship between A (AO) sampled as shown in Figure 18 and we estimate Iq. The function estimation unit 28 emits the variation A (AO) of the current position change with respect to Iq based on the estimated function. The sum of O (Tn) - O (Tn-1) = AG and the output A (AO) of the function estimation unit 28 is issued by the adder / subtractor 29 and the position change during the delay time Td is obtained by multiplying its output by Td / T0. The change in position obtained is added to O (Tn) by the adder 24 to compensate for the delay time. The function to be estimated by the function estimation unit 28 can be a function of the second degree or a higher degree. Thus, according to the sixth embodiment, the means for compensating the output of the encoder therefore evaluates in advance a relationship between a value of the current which must be emitted by the drive unit.

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  of the motor and a degree of variation of the position change in the sampling cycle, the position change that occurs during the delay time is predicted from the evaluated relationship, the current value of the current and the position data . By compensating the position data in this way, more precise output position data is obtained. Seventh embodiment Fig. 19 is a configuration diagram of the encoder unit according to a seventh embodiment of the present invention. In FIG. 19, the components which are common with the encoder unit represented in FIG. 1 are designated by the same reference numbers and we omit to give their

  description. One LED includes 4A and 4B and

  6C and 6D light receiving devices are added. The drawings of the stop plate 5 are formed in parallel to generate analog signals and pulse train signals as shown in Figure 20. In Figure 20, the shaded portion intercepts light. The analog signals which must be emitted by the light receiving devices 6A and 6B are converted into position data O (Tn) which will be processed as in the classic example. The pulses of the pulse trains A and B which must be emitted by the light receiving devices 6C and 6D have a phase difference of 90 and they are counted by the reversible counter 30. Figure 21 shows the data processing timings of the encoder unit shown in FIG. 19. The reversible counter 30 is reset to zero at the same time as the sampling and holding circuits 7A and 73 maintain the sampling data and, then, it counts the pulses

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  A and B. The A / D conversion time and the arithmetic processing time Td are compensated for by adding the count number AO (Td) of the counter 30 during the time Td until the arithmetic processing of the unit is completed. arithmetic 9 at the output of the arithmetic unit 9 in the adder 24. The configuration as described above makes it possible to transmit these data in a state devoid of delay time. A change of position for the time necessary for the serial exit can be estimated from AO (Td) and the change of position carried out

  during the communication time can be compensated.

  Thus, according to the seventh embodiment, the encoder unit which samples analog signals according to an angle of rotation of the rotating shaft and obtains the angle of rotation of the rotating shaft from converted digital data , is equipped with: pulsed signal generating means intended to generate two trains of pulses having pulses whose phases are offset by 90 relative to each other; a counter for counting a number of pulses of the pulse trains to measure a delay angle of rotation of which said shaft rotates for a period of time requested by the A / D converter to sample the analog signals and by means of arithmetic operation to determine the angle of rotation; and encoder output compensation means for outputting a current angle represented by the sum of the rotation angle and the delay rotation angle. The encoder unit can exactly compensate for the delay time required for A / D conversion and for arithmetic processing, regardless of the behavior of motor speed and acceleration, and the increase in

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  control loop delay and error of the

  magnetic pole detection can be eliminated.

* As described above, a servo unit according to the present invention comprises an encoder unit intended to sample the analog signals according to a position of the object to be detected and to obtain position data from the converted digital data. The encoder unit includes an encoder output compensation unit which predicts a change in position of the object to be detected during the delay time requested to sample the analog signals and transmit the position data. The encoder output compensation unit uses position data obtained from the current sample and position data obtained from previous samplings, and outputs the predicted position change as well as precise position data obtained by adding the predicted position change to the position data obtained from the current sampling. The encoder output compensation unit also outputs the position data obtained from the current sampling (uncompensated). Since in the present invention it is acceptable that the delay time required for A / D conversion, arithmetic processing and communication is relatively long, an A / D conversion means and a means of communication can be used. inexpensive arithmetic operation. The arithmetic operation means and the output compensation means can be realized with a central processing unit (CPU) and a microprocessor unit (MPU) respectively; the increase in cost of the exit compensation means can therefore be eliminated. In addition, for example, communication

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  with the motor drive unit does not have to be

excessively accelerated.

  The servomotor control unit according to the present invention further comprises: a motor drive unit for driving the servomotor which is equipped with position control means; speed control means; a means of conversion; current control means and voltage control means. A speed order value is generated by the position control means with a low loop gain as a function of the difference between the position order value and the currently sampled position data that the encoder unit transmits. A current order value is generated by the speed control means with a high loop gain as a function of a difference between a speed order value and the speed reaction value obtained from the change of position. predicted from the encoder unit. A three-phase alternating current detected on the servomotor is converted into a torque component current, using predicted position data. The voltage order value is generated as a function of a difference between a current order value and a current reaction value (the torque component current) (for conversion in response to the current position of the poles magnetic when the servomotor is a synchronous motor) input by the conversion means. A three-phase voltage is generated in response to the current position of the magnetic poles based on the voltage order value and the predicted position data. In this way, the actuator can be controlled precisely without any increase in the vibration or the irregularity of speed of the actuator.

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Claims (9)

  A servomotor control unit comprising: an encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensating means (11) which uses the position data obtained from the current sampling and previous samples to predict a change in position of the detected object which occurs during a time of delay required to sample the analog signals and transmit the position data, said encoder output compensation means generating the predicted position data by adding the predicted position change to the currently sampled position data; a servomotor (3); and a motor drive unit (2) comprising: position control means (13) for generating a speed command value in response to a difference between a position command value and the position data currently sampled; speed control means (15) for generating a current order value in response to a difference between said speed order value and a speed reaction value obtained from the predicted change in position; conversion means for converting alternating current SR 11263 JP / JCI   three-phase detected on the servomotor (3) in a torque component current, according to a current position of magnetic poles; current control means (17) for generating a voltage command value in response to a difference between said current command value and a current reaction value related to a torque component current entered by said means of conversion; and voltage generating means (18) for outputting three-phase voltage in response to the voltage order value and a current position of magnetic poles based on the data predicted positions.   2. Unit according to claim 1, characterized in   that the servomotor (3) is a synchronous motor.   3. Encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensating means (11) which uses the position data obtained from the current sampling and previous samples to predict a change in position of the detected object which occurs during a time of delay required to sample the analog signals and transmit the position data, said encoder output compensation means generating the predicted position data by adding the predicted position change to the currently sampled position data; SR 11263 JP / JCI   characterized in that said encoder output compensating means (11) predicts the predicted position change by selecting the smallest of the following values: the absolute value of a position change which occurs during a current sampling cycle and the absolute value of a position change that occurred during a previous sampling cycle, and assuming that the position changes that occurred during the sampling cycles are in linear or curvilinear relationship to the change of selected position.   4. Encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling the analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensating means (11) which uses the position data obtained from the current sampling and previous samples to predict a change in position of the detected object which occurs during a time of delay required to sample the analog signals and transmit the position data, said encoder output compensation means generating the predicted position data by adding the predicted position change to the currently sampled position data; characterized in that said encoder output compensation means (11) predicts the change in SR 11263 JP / JCI   predicted position by selecting the smallest of the following values: the absolute value of a position change that occurs during a current sampling cycle and the absolute value of a position change that occurs during a sampling cycle previous sampling, and selecting the smallest of the following differences: the difference between a change of position that occurs during the current sampling cycle and a change of position that occurred during the previous sampling cycle; and the difference between the change of position that occurred during the previous sampling cycle and the change of position that occurred during a sampling cycle that preceded the previous sampling cycle, and assuming that position changes that occur during sampling cycles are linear or curvilinear in relation to the sum of the selected position change and the selected difference between position changes.   5. Encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling the analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensation means (11) which uses position data obtained from the current sampling and previous samples to predict a SR 11263 JP / JCI   change in position of the detected object which occurs during a delay time necessary to sample the analog signals and transmit the position data, said means for compensating the output of the encoder generating the predicted position data by adding the change in position predicts the currently sampled position data; characterized in that said encoder output compensation means (11) predicts the predicted position change assuming that the position changes which occur during sampling cycles are in linear or curvilinear relationship to the mean value of a position change that occurs during a current sampling cycle and a position change that occurs during a previous sampling cycle. 6. Encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling the analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensating means (11) which uses the position data obtained from the current sampling and previous samples to predict a change in position of the detected object which occurs during a time of delay required to sample the analog signals and transmit the position data, said means for compensating the SR 11263 JP / JCI   output of the encoder generating the predicted position data by adding the predicted position change to the currently sampled position data; characterized in that said encoder output compensation means (11) predicts the predicted position change assuming that the position changes which occur during the sampling cycles are in linear or curvilinear relationship to the sum of: the average value of a change of position that occurred during a current sampling cycle and a change of position that occurred during a previous sampling cycle; and the average value of the difference between the change of position that occurred during the current sampling cycle and the change of position that occurred during the previous sampling cycle, and the difference between the change of position that occurred during the previous sampling cycle and the change in position that occurred during a sampling cycle that preceded the cycle previous sampling.   7. Encoder unit (1) comprising: signal generating means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling the analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and an encoder output compensation means (11) which uses the position data obtained from the current sampling and SR 11263 JP / JCI   of previous samplings to predict a change in position of the detected object which occurs during a delay time necessary to sample the analog signals and transmit the position data, said means for compensating the output of the encoder generating the position data predicted by adding the predicted position change to currently sampled position data; characterized in that said encoder output compensation means (11) predicts the predicted position change based on the position data obtained from the current sampling cycle and previous sampling cycles, and in that it includes a variable multiplier (27) which reduces the predicted position change when the position change in the current sampling cycle is small. 8. Encoder unit (1) comprising: signal generator means for generating analog signals according to the position of a detected object; A / D conversion means (8) for sampling the analog signals and converting the analog signals to digital data; arithmetic operation means (9) for generating position data of the detected object from the digital data; and encoder output compensation means (11) which uses the position data obtained from the current sampling and previous samples to predict a change in position of the detected object which occurs during a time of delay required to sample the analog signals and transmit the position data, said means for compensating the SR 11263 JP / JCI   output of the encoder generating the predicted position data by adding the predicted position change to the currently sampled position data; characterized in that said encoder output compensation means (11) evaluates in advance a relationship between a current value to be emitted by a motor drive unit (2) and a degree of variation of the changes position produced during the sampling cycles, and predicts the predicted position change based on the evaluated relationship and the current value of the current and position data.   9. Encoder unit (1) comprising: signal generator means for generating analog signals which correspond to an angle of rotation of a rotating shaft; A / D conversion means (8) for sampling said analog signals and converting said analog signals to digital data; arithmetic operation means (9) for determining an angle of rotation of said rotating shaft from the digital data; pulsed signal generating means for generating two pulse trains having pulses whose phases are offset by 90 relative to each other; a counter (30) for counting a number of said pulses of said pulse trains to measure a delay rotation angle of which said shaft rotates for a period of time requested by said A / D conversion means (8) for sampling said signals analog and by the arithmetic operation means (9) for determining said angle of rotation; and SR 11263 JP / JCI   encoder output compensating means (11) for emitting a current angle as a sum of said angle of rotation and said angle of delay rotation. SR 11263 JP / JCI